import java.util.Scanner;
public class Test2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (true) {
            System.out.print("请输入学生的成绩（0-100）：");
            int score = scanner.nextInt();
            if (score >= 0 && score <= 100) {
                if (score >= 90) {
                    System.out.println("优等生");
                } else if (score >= 60) {
                    System.out.println("良等生");
                } else {
                    System.out.println("差等生");
                }
            } else {
                System.out.println("成绩无效！请输入0到100之间的数字。");
            }
        }
    }
}